Hydrogen transfer catalyst

ABSTRACT

A NOVEL CATALYST SYSTEM INCLUDING AN ACTIVE METAL OXIDE SELECTED FROM THE GROUP CONSISTING OF NOBEL METALS AND NICKEL; AND PROMOTER SELECTED FROM THE GROUP CONSISTING OF TIN AND LEAD; IF DESIRED, A SECOND PROMOTER SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS, SUCH AS POTASSIUM, RUBIDIUM, SECIUM, ETC., A ALKALINE EARTH METAL, SUCH A CALCIUM, STRONTIUM, BARIUM, ETC., AND A RARE EARTH METAL, SUCH AS CERIUM, THROIUM, ETC., AND AN INERT OXIDE SUPPORT, SUCH AS ALUMINA. THE SUBJECT CATALYST CATALYSTS ARE UTILIZED IN THE HYDRODEALKYLATION OF ALKYL AROMATICS, ETC., IN THE DEHYDROGENSTION OF PARAFFINS AND THE LIKE, AND IN THE DEHYDROGENATION-DESULFURIZATION OF SULFUR- AND NITROGEN-COTAMINATED HYDROCARBON MATERIALS.

United States Patent US. Cl. 252-462 3 Claims ABSTRACT OF THE DISCLOSUREA novel catalyst system including an active metal oxide selected fromthe group consisting of noble metals and nickel; a promoter selectedfrom the group consisting of tin and lead; if desired, a second promoterselected from the group consisting of alkali metals, such as potassium,rubidium, cesium, etc., an alkaline earth metal, such as calcium,strontium, barium, etc., and a rare earth metal, such as cerium,thorium, etc.; and an inert oxide support, such as alumina. The subjectcatalysts are utilized in the hydrodealkylation of alkyl aromatics,etc., in the dehydrogenation ofparatfins and the like, and in thedehydrogenation-desulfurization of sulfurand nitrogen-contaminatedhydrocarbon materials.

BACKROUND OF THE INVENTION This is a division of application Ser. No.769,737 filed Oct. 22, 1968 now US. Pat. 3,686,340.

The present invention relates to novel catalyst compositions,particularly useful for the catalysis of hydrogen transfer reactions andnovel processes for the utilization of such catalysts. In a morespecific aspect, the present invention relates to novel catalystcompositions particularly useful for the conduct of hydrodealkylationreactions, dehydrogenation reactions, and hydrogenation-hydrotreatingreactions, and such reactions utilizing these catalysts.

In recent years, the demand for hydrocarbon fuels and chemicals derivedfrom hydrocarbons has increased at such a rapid rate and the domesticsupply of petroleum crude oils had diminished to the point that it hasbecome necessary to convert low grade petroleum crude oils to fuels andchemicals, to upgrade refinery streams not heretofore utilized for highgrade fuels and chemicals and to utilize hydrocarbon liquids, alsousually of low grade, derived from coal by carbonization and solventextraction, from oil shales, and from tar sands. One of the primaryoperations for the upgrading of low grade hydrocarbons is a group ofreactions involving changing the carbon to hydrogen ratio or displacinga substituent group with hydrogen. The change in the carbon to hydrogenratio may be effected by dehydrogenation as, for example, in thedehydrogenation of parafiins to corresponding mono-olefins, in thedehydrogenation of paraffins and mono-olefins to diolefins; or in thedehydrogenation of paraflins or cycloparafiins to aromatics, or thechange may be effected by hydrogenation as, for example, in thehydrogenation of diisobutylene to isooctane and in the hydrogenation ofunsaturated polymer gasoline into motor fuels of less unsaturatedcharacter and the like. In certain instances, such changes in the carbonto hydrogen ratio may be accompanied to some extent by isomerizationtype reactions, such as those involved in the cyclization of parafiinichydrocarbons, such as the conversion of hexane to benzene, etc. In someinstances, also, the hydrogen displaces substituent groups, particularlysubstituent groups of cyclic hydrocarbons; for example, in thedealkylation of alkyl aromatics, etc. De-

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structive conversion of organic sulfur and nitrogen compounds found insome hydrocarbon materials and the saturation of highly unsaturatedmaterials may also be effected.

One particularly useful reaction of this type is the hydrodealkylationof alkyl aromatics to convert toluene to benzene, and coal tar lightoils and coal tar methyl naphthalene to benzene and naphthalene,respectively. The thermal version of this process requires extremelyhigh temperatures and pressures. The catalytioprocess generally employsa chromia-magnesia catalyst deposited on an alumina base, but, in spiteof the effectiveness of this catalyst, it requires high temperatures,high hydrogen pressures and suffers from low yields, low selectivity andrapid degeneration of the catalyst.

Another highly valuable reaction of this character is a dehydrogenationprocess which converts parafiins to olefins. etc. While severalprocesses have been developed for this purpose, these processes havevery short onstream times, they are cyclic, adiabatic, fixed-bedoperations and necessitate frequent regeneration of the catalyst due tocarbon lay-down and catalyst fouling. Catalyst deactivation is alsoquite prounounced.

Another process of extreme importance when dealing with low gradehydrocarbon liquids, particularly those containing substantial volumesof sulfur and nitrogen and their compounds is thehydrogenation-hydrotreating of such materials. While certain catalystshave heretofore been developed for this type of operation, none appearto have qualities necessary to simultaneously desulfurize anddenitrogenate the crudes and add hydrogen to the aromatic and olefiniccompounds contained in the feed materials. In other words, somecatalysts have heretofore been useful in desulfurizing anddenitrogenating but are highly ineffective for the hydrogenation portionof the reaction; whereas, those useful for hydrogenation are readilypoisoned by the desulfurization and denitrogenation. Again, in this areaof operation, there is a tendency for the catalyst to rapidly degenerateand become coked, thereby losing its activity quite rapidly.

It is therefore an object of the present invention to provide animproved catalyst for overcoming substantially all of the abovementioned difficulties. In a more specific aspect, the present inventionrelates to a novel catalyst system for carrying out hydrogen transferreactions. Still another object of thepresent invention is to provide animproved catalyst system for hydrogen transfer reactions which requiresrelatively low temperatures. Another object of the present invention isto provide an improved catalyst system for hydrogen transfer reactionswhich requires relatively low hydrogen pressures. Another object of thepresent invention is to provide an improved catalyst system for hydrogentransfer reactions which produce high product yields. Another andfurther object of the present invention is to provide an improvedcatalyst system for hydrogen transfer reactions which exhibits a highselectivity to the desired reaction. Yet another object of the presentinvention is to provide an improved catalyst system for hydrogentransfer reactions which is highly resistant to coking. Another objectof the present invention is to provide an improved catalyst system andprocess for the hydrodealkylation of alkyl aromatics. Another andfurther object of the present invention is to provide an improvedcatalyst system and process for the dehydrogenation of paraflinichydrocarbons. Still another object of the present invention is toprovide an improved system and process for thehydrogenation-dehydrogenation of hydrocarbon materials contaminated withsulfur and nitrogen. These and other objects and advantages of thepresent invention will be apparent from the following description.

3 SUMMARY on THE INVENTION Briefly, in accordance with the presentinvention, the novel catalyst composition of the present inventionincludes an active metal of Group VIII selected from the groupconsisting of noble metals and nickel, a promoter of a Group IV metalselected from the group consisting of tin and lead and an inert carriermaterial. More specifically, the noble metals of Group VIH, and nickel,in their oxide forms are deposited on an inert oxide carrier along withtin or lead in their oxide form. The catalysts are further improved byadding to the Group VIII and Group IV metals an alkali metal, analkaline earth metal, or a rare earth metal as a second promoter. Novelhydrogen transfer reactions utilizing the above catalytic materials arealso taught herein.

The novel catalysts of the present invention include a Group VIII metalin its oxide form, including specifically ruthenium, rhodium, palladiumand platinum of the noble metal group, and nickel from the non-noblemetal or ferrous group of Group VIII. The promoter from Group IVparticularly includes tin and lead oxides. Where a second promoter isutilized, a metal or mixture of metals selected from the groupconsisting of alkali metals, alkaline earth metals and rare earth metalsmay be utilized. These materials are also in their oxide forms andinclude potassium, rubidium, cesium, calcium, strontium, barium, cerium,thorium, and the like. The inert oxide support is preferably a gammaalumina, including the beta, eta, boehmite and bayerite, etc.,crystalline forms. Other inert oxide supports include other aluminas,silica-alumina, silica, silica-magnesia, alumina-magnesia,silica-zircon-ia, etc.

In the preparation of the novel catalysts of the present invention,well-known techniques may be employed. These include, for example,coprecipitation and impregnation techniques. The base material may be anextrudate or pellet to be impregnated or a powder which is thereafterpelletized or extruded to yield the finished catalyst. The active metalportion of the catalyst and the promoters are added through the use ofwater-soluble salts such as their halides, nitrates, sulfates, acetates,etc. Easily hydrolyzed salts can be kept in solution withoutdecomposition by employing an appropriate inorganic acid, for example,sulfuric acid for tin sulfate, hydrochloric acid for tin chloride, etc.Drying and calcination of the catalyst can be employed, for examplevacuum drying, and calcination in oxidative, neutral or reductiveatmospheres employing temperatures of about 800 to 1200 F.

The following examples are illustrative of accepted techniques forpreparing the novel catalysts of the present application. Example I To900 ml. of distilled water was added 40 g. of stannous sulfate and 15ml. of concentrated sulfuric acid. The sulfuric acid was required tobring the insolubles from the stannous sulfate into solution. This wasbelieved to be tin hydroxide. This solution was added to 900 ml. of aboehmite alumina as pellets and after contact for fifteen minutes, theunadsorbed liquid was decanted from the catalyst pellets. The resultingimpregnated catalyst was dried at 250 F. for one hour and calcined inair at 950 F. in a mufile furnace for sixteen hours. This yielded acatalyst of the following composition:

A solution containing 150 m1. of distilled water and 2 g. of rhodiumtrichloride was added to 150 ml. of 2% SnO--'Al O pellets from above.Catalyst and solution was in contact for fifteen minutes and theunadsorbed liquid was decanted. The resulting catalyst was dried at 250F. for one hour and calcined in air at 950 in a mufile furnace forsixteen hours. This yielded a catalyst of the following composition:

1% 'Rh--2% sac-A1 0,

A solution containing ml. of distilled water and 5.5 g. of cesiumnitrate was added to 150 ml. of 1% 'Rh-2%SnO-Alg0 pellets from above.Catalyst and solution was in contact for fifteen minutes and theunadsorbed liquid was decanted. The resulting catalyst was dried at 250F. for one hour and calcined in air at 950 F. in a mufile furnace forsixteen hours. This yielded a catalyst of the following composition:

By employing the techniques and procedures outlined in Example I, othercatalytic compositions were prepared. A solution containing I150 ml. ofdistilled water and 67 g. of a 5% palladium (ous) chloride solution wasadded to 150 ml. of 2% SnOAl O pellets prepared in Example I. Drying andcalcination yielded the following composition:

A solution containing 150 ml. of distilled water and 5.5 g. of cesiumnitrate was added to 150 ml. of 1% Pd2% SnO--Al O pellets from above.Drying and calcination yielded the following composition:

1% Pd2% Cs O2% SnO-Al O Example III To 600 ml. of distilled water wasadded 54 g. of stannous sulfate and 20 ml. of concentrated sulfuricacid. The tin sulfate was partially insoluble and the sulfuric acidbrought it into solution. This insolubility was probably due to thepresence of tin hydroxide. This solution was added to 600 ml. of aboehmite alumina and after contact for fifteen minutes the unadsorbedliquid was decanted from the catalyst pellets. The resulting impregnatedcatalyst was dried at 250 F. for one hour and calcined at 950 F. in airin a mufile furnace for sixteen hours. This yielded a catalyst of thefollowing composition:

A solution containing 150 ml. of distilled water and 4.5 g. ofchloroplatinic acid was added to 150 ml. of 4% SnOAl O pellets (preparedas above) and allowed to remain in contact for fifteen minutes beforedecanting the unadsorbed liquid. The impregnated catalyst was dried at250 F. for one hour and calcined in air at 950 F. for sixteen hours in amuffie furnace. This yielded a catalyst of the following composition:

1% Pt4% SnO--Al O Example IV By employing the technique and procedureoutlined in Example III, 1% Rh4% SnOAl O' and 1% Ru4% SnOAl O wereprepared by utilizing rhodium trichloride and ruthenium trichloride,respectively.

Optimum contents of the Group VIII metal include 0.5-5% by weight basedon the finished catalyst, while the promoter concentration variesbetween 1 and 15% by weight.

As previously pointed out, the catalysts of the present application areparticularly useful in carrying out the hydrodealkylation of alkylaromatics to produce the parent aromatic hydrocarbons. Feedstocks forsuch process include toluene and polymethyl benzenes, coal tar lightoils, coal tar methyl naphthalene concentrates, and bicyclicconcentrates from light cycle oils and heavy reformates. Feedstockpreparation can include fractionation to remove front ends or bottoms,thereby removing undesired fractions, such as unsaturates, indanes andresinous materials. The distillation may be preceded or followed by ahydrogenation-hydrotreating step. Feedstocks with or without sulfur canbe processed over the catalysts of the present invention. It ispreferred, however, to employ a trace of sulfur to lOO ppm.) in order toreduce hydrocrack- TABLE H lng activity wlthout hindering thehydrodealkylation ac- Run 8 9 trvrty of the catalyst. The processingconditions for the hydrodealkylation re- Catalyst 12Cr-2Mg"A123IRAQI-A1203 action of the present invention include a temperature be-Prodngt difitgiglution: 3 3

ap t ene 7. 8 9. 9 tween about 1050 and 1200 F., a pressure betweenabout Naphthalene 5% 521 100 and 1000 p.s.1.g., a liquid hourly spacevelocity begletlg'lliwightlfiilfinlzg.-- g 2% 1m 9, a tween about 0.1and 5, and a hydrogen-to-hydrocarbon wt pe,centeedPMeN conversion 90 86mole ratio of about 3 to 15/ 1. 2:23 011 catalyst: Percent 1 32 o 39 Inorder to illustrate the hydrodealkylation ability of the catalysts ofthe present invention, a series of Runs was see the table made in whichtoluene was hydrodealkylated at 1150 F., Wt. percent 500 p.s.i.g., 0.5LHSV, and a 5:1 hydrogen to hydrocar- Naphtha1ene 50,4 bon ratio. TheTable below gives the results of these Runs Naphthalene fig: as comparedwith runs utilizing a commercial chromiamagnesia on alumina catalyst.TABLE 1' Run 1 2 3 4 5 6 7 Catalyst 12Cr-2Mg-A1z0s lRh-ZCS-ZSIl-AleOalPd-2Cs-2Sn-Alz0e lPt-4Sn-Alz0; 1Rh-4Sn-Alg0 1Ru-4Sn-Alg0 Feed: Sulfur,p p m 130 Liquid recovery, vol. percent feed 84 84 58 s4 s2 s3 s3. 3Product distribution:

Benzene 0. 8 0. 7 0. 2 0. 8 0. 5 O. 8 0. 3 Benzene 66.8 66.7 90.3 74.071.6 73.5 39.5 Toluene 32. 4 32. 6 7. 3 25. 2 27. 9 25. 7 60. 2 Wt.percent feed:

Toluene conversion. 72.8 72. 7 95. 8 78. 8 77. 2 78. 7 46. 9 Selectivityto benzene... 92 92 66 95 91 93 88 Carbon on catalyst: wt. percent feed0 26 0. 06 0. 09 0.06 0.13 0.05 o

The chromia-magnesia catalyst used in the comparison is a commercialhydrodealkylation catalyst which is probably the most widely used in theindustry. It is apparent, however, that catalysts of this inventionresult in higher conversion rates at comparable selectivities and havelower coking rates. The lower coking rates, of course, insures longeron-stream catalyst life and lower operating temperatures. The truecoking rate of the commercial catalyst is not evident from the data. Inactual practice, this catalyst is completely deactivated by coke withinseveral days and to maintain conversion, operating temperatures must beraised to about 1300-1350 F. as the catalyst ages. Secondly, highhydrogen partial pressures must be maintained to control the increase incoking with elevation in operating temperatures. By contrast, thecatalysts of the present invention maintain a low coking rate,conversion remains constant with carbon deposition on the catalyst, andlower hydrogen ratios can be utilized.

In other studies of the above catalysts, it was found that coal tarmethylnaphthalene concentrates, as received from the coke oven, containlarge amounts of resinous materials. However, by distilling theseconcentrates to yield a 90% overhead fraction, polymers, resins and freecarbon may be removed as a bottoms fraction. By thus pretreating theseconcentrates, the carbon lay-down on the hydrodealkylation catalyst isfurther reduced and hydrogen consumption due to hydrocracking of theresins and polymers is reduced.

The following Table II illustrates the effect of a catalyst of thepresent invention as compared with a commercial chromia-magnesiacatalyst when utilized in the hydrodealkylation of coal tarmethylnaphthalenes. The conditions employed included a temperature of1100 F., a pressure of 500 p.s.i..g., a liquid hourly space velocity of0.5 and a hydrogen-to-hydrocarbon mole ratio of 5:1.

Table III shows the use of a catalyst of this invention on a differentfeed under the same conditions.

Me Naphthalene Di Me Naphthalene Carbon on Catalyst-Wt. Percent Feed0.22

The advantages of the process of the present invention are furtherillustrated by a series of tests conducted for the hydrodealkylation oftoluene in the presence of the novel catalysts of the present invention.Specifically, in the tests set forth in the following Table, a noblemetal was combined with lead in one instance and this catalystthereafter had a rare earth metal added thereto in a second test.

TABLE IV Conditions: 1,150 F., 500 p.s.l.g., 0.5 LHSV, 5/1 Hz/H'C Feed:Toluene Run 11 12 Catalyst 1 Pd-4 Pb 1 Pd-l Cs A120; 4 Pia-A120;

Liquid recovery, v01. percent feed 81. 5 85.0 Product distribution:

Benzene 0. 5 0. 3

Benzene.- 54. 2 48. 1

Toluene 46. 3 51. 6 Wt. percent feed:

Toluene conversion 62. 2 55. 9

Selectivity to benzene 88 Carbon on catalyst: wt. percent feed 095 003Suitable conditions for the operation of the hydrogenation-hydrotreatingprocess of the present invention include a temperature of about 500 to900 F., a pressure of about 100 to 3000 p.s.i.g., a liquid hourly spacevelocity between about 0.1 and 10, and a hydrogen-to-hydrocarbon moleratio of about 3 to 15/1.

When reference is made herein to the Periodic System of elements, theparticular groupings referred to are as set forth in the Periodic Chartof the Elements in The Merck Index, Seventh Edition, Merck & Co., Inc.,1960.

We claim:

1. A catalyst composition consisting essentially of between about 0.5and about 5 percent by weight of nickel oxide and a promoting amount oflead oxide, both deposited on an inert oxide support.

2. A catalyst in accordance with claim 1 wherein the inert oxide supportis a gamma alumina.

3. A catalyst composition consisting essentially of between about 0.5and about 5 percent by weight of an oxide of a metal selected from thegroup consisting of ruthenium, rhodium, palladium and nickel, andpromoting amounts of lead oxide and of an oxide a metal selected fromthe group consisting of potassium, rubidium, cesium,

calcium, strontium, barium, cerium, thorium, and mixtures thereof, alldeposited on an inert oxide support.

References Cited UNITED STATES PATENTS 2,999,074 9/1961 Bloch et al.252442 3,480,053 11/1969 Mulaskey 252466 J 3,531,543 9/1970 Cuppinger etal. 252466 J 3,682,118 8/1972 Mulaskey 252466 J 3,425,792 2/ 1969Stephens 252466 J 3,580,970 5/1971 Swift 252466 J FOREIGN PATENTS1,003,499 9/ 1965 Great Britain 252466 PT DANIEL E. WYMAN, PrimaryExaminer W. J. SHlNE, Assistant Examiner US. Cl. X.R.

252459, 466 I, 466 PT, 472, 473, 474

